The present invention relates to magnetoresistive random-access memory (MRAM), and more specifically, to a double magnetic tunnel junction (DMTJ) with a dynamic reference layer.
MRAM is a non-volatile memory that combines a magnetic device with standard silicon-based microelectronics. Data is stored in MRAM as magnetic states or characteristics (e.g., polarity or magnetic moment) instead of electric charges. In a typical configuration, each MRAM cell includes a transistor, a magnetic tunnel junction (MTJ) device (i.e., memory cell) for data storage, a bit line and a word line. A typical MTJ structure includes a stacked configuration having a fixed magnetic layer, a thin dielectric tunnel barrier, and a free magnetic layer. The MTJ has a low resistance when the magnetic moment of its free layer is parallel to the magnetic moment of its fixed layer. Conversely, the MTJ has a high resistance when its free layer magnetic moment is oriented anti-parallel to its fixed layer magnetic moment. The MTJ can be read by activating its associated word line transistor, which switches current from a bit line through the MTJ. The MTJ resistance can be determined from the sensed current, which is itself based on the polarity of the free layer. Conventionally, if the fixed layer and free layer have the same polarity, the resistance is low and a “0” is read/written. If the fixed layer and free layer have opposite polarity, the resistance is higher and a “1” is read/written.